add descriptive error if no free volumes

weed/server/master_grpc_server_volume.go

@@ -77,7 +77,7 @@ func (ms *MasterServer) Assign(ctx context.Context, req *master_pb.AssignRequest
 
 	if !ms.Topo.HasWritableVolume(option) {
 		if ms.Topo.AvailableSpaceFor(option) <= 0 {
-			return nil, fmt.Errorf("No free volumes left!")
+			return nil, fmt.Errorf("no free volumes left for "+option.String())
 		}
 		ms.vgLock.Lock()
 		if !ms.Topo.HasWritableVolume(option) {

weed/server/master_server_handlers.go

@@ -113,7 +113,7 @@ func (ms *MasterServer) dirAssignHandler(w http.ResponseWriter, r *http.Request)
 
 	if !ms.Topo.HasWritableVolume(option) {
 		if ms.Topo.AvailableSpaceFor(option) <= 0 {
-			writeJsonQuiet(w, r, http.StatusNotFound, operation.AssignResult{Error: "No free volumes left!"})
+			writeJsonQuiet(w, r, http.StatusNotFound, operation.AssignResult{Error: "No free volumes left for " + option.String()})
 			return
 		}
 		ms.vgLock.Lock()

weed/storage/super_block/replica_placement.go

@@ -6,9 +6,9 @@ import (
 )
 
 type ReplicaPlacement struct {
-	SameRackCount       int
-	DiffRackCount       int
-	DiffDataCenterCount int
+	SameRackCount       int `json:"node,omitempty"`
+	DiffRackCount       int `json:"rack,omitempty"`
+	DiffDataCenterCount int `json:"dc,omitempty"`
 }
 
 func NewReplicaPlacementFromString(t string) (*ReplicaPlacement, error) {

weed/topology/volume_growth.go

@@ -1,6 +1,7 @@
 package topology
 
 import (
+	"encoding/json"
 	"fmt"
 	"github.com/chrislusf/seaweedfs/weed/storage/types"
 	"math/rand"
@@ -25,15 +26,15 @@ This package is created to resolve these replica placement issues:
 */
 
 type VolumeGrowOption struct {
-	Collection         string
-	ReplicaPlacement   *super_block.ReplicaPlacement
-	Ttl                *needle.TTL
-	DiskType           types.DiskType
-	Prealloacte        int64
-	DataCenter         string
-	Rack               string
-	DataNode           string
-	MemoryMapMaxSizeMb uint32
+	Collection         string                        `json:"collection,omitempty"`
+	ReplicaPlacement   *super_block.ReplicaPlacement `json:"replication,omitempty"`
+	Ttl                *needle.TTL                   `json:"ttl,omitempty"`
+	DiskType           types.DiskType                `json:"disk,omitempty"`
+	Prealloacte        int64                         `json:"prealloacte,omitempty"`
+	DataCenter         string                        `json:"dataCenter,omitempty"`
+	Rack               string                        `json:"rack,omitempty"`
+	DataNode           string                        `json:"dataNode,omitempty"`
+	MemoryMapMaxSizeMb uint32                        `json:"memoryMapMaxSizeMb,omitempty"`
 }
 
 type VolumeGrowth struct {
@@ -41,7 +42,8 @@ type VolumeGrowth struct {
 }
 
 func (o *VolumeGrowOption) String() string {
-	return fmt.Sprintf("Collection:%s, ReplicaPlacement:%v, Ttl:%v, DataCenter:%s, Rack:%s, DataNode:%s", o.Collection, o.ReplicaPlacement, o.Ttl, o.DataCenter, o.Rack, o.DataNode)
+	blob, _ := json.Marshal(o)
+	return string(blob)
 }
 
 func NewDefaultVolumeGrowth() *VolumeGrowth {